Mysqli db class

/**
 * Database connection class.
 * $db = new db(array(host, user, password, database));
 * $db->connect();
 * $clean = $db->clean($dirty);
 * $db->query("");
 * $db->disconnect();
 */
class db {

    private $db = array();
    private $connection;

    public function db($args = array()) {
        $this->db['server']     = $args['server'];
        $this->db['username']   = $args['username'];
        $this->db['password']   = $args['password'];
        $this->db['database']   = $args['database']; }

    public function connect() {
        $this->connection = mysqli_connect($this->db["server"], $this->db["username"], $this->db["password"]);
        $this->select_db(); }

    public function disconnect() {
        mysqli_close($this->connection);
        $this->connection = null; }

    public function select_db() {
        mysqli_select_db($this->connection, $this->db["database"]); }

    public function query($sql) {
        $this->result = mysqli_query($this->connection, $sql); }

    public function is_connected() {
        return ($this->connection) ? true : false; }

    public function clean($dirty) {
        if (!is_array($dirty)) {
            $dirty = ereg_replace("[\'\")(;|`,<>]", "", $dirty);
            $dirty = mysqli_real_escape_string($this->connection, trim($dirty));
            $clean = stripslashes($dirty);
            return $clean; };
        $clean = array();
        foreach ($dirty as $p=>$data) {
            $data = ereg_replace("[\'\")(;|`,<>]", "", $data);
            $data = mysqli_real_escape_string($this->connection, trim($data));
            $data = stripslashes($data);
            $clean[$p] = $data; };
    return $clean; }

}